A double-acting fluid-dynamic actuator comprises a cylinder and a piston, which is movable inside the cylinder under the action of a pressurized fluid and is provided with a head that sealingly slides along the inside walls of the cylinder and a rod integral with the head.
A system for determining the position of a piston along its path of travel for a fluid-dynamic actuator of the type described above is known in the prior art. Said system normally comprises a magnetostrictive sensor suitable to be mounted with a first part on the rod and with a second part on the cylinder. In particular, the magnetostrictive sensor comprises a magnet that is mounted along the cylinder to generate an electromagnetic field through the rod and an element sensitive to the electromagnetic field inserted in a specific seat obtained inside the rod and connected electrically to a control unit. This type of sensor requires complex and expensive machining processes to produce both the cylinder and the rod of the piston.
Another known system for determining the position of a piston along its path of travel comprises an optical sensor and a decoding unit to read a series of binary codes on the rod, each consisting of a series of grooves, arranged according to a specific pattern that defines the code, on the outer surface of the rod transversely with respect to the longitudinal axis of the rod. The precision of the system is defined by the size of the grooves and the precision with which they are machined on the rod. This system has the advantage, compared to that using the magnetostrictive sensor, of not requiring any specific machining of the cylinder, but it still requires special and expensive machining of the rod to obtain good reading accuracy.